package org.wjw.udp;

import java.io.IOException;
import java.net.BindException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;
import java.nio.charset.StandardCharsets;

@SuppressWarnings("InfiniteLoopStatement")
public class UDPEchoServer {

    //声明一个udp服务对象
    private DatagramSocket socket;

    //通过构造方法来指定服务端口号
    public UDPEchoServer(int port) throws SocketException {
        if (port < 1 || port > 65535) {
            throw new BindException("端口号建议在 1025 - 65535之间");
        }
        //实例化udp服务
        this.socket = new DatagramSocket(port);
    }

    //启动服务
    public void start() throws IOException {
        System.out.println("服务器启动成功");
        //循环处理请求
        while (true){
            //1. 使用DatagramPacket来接收用户的请求
            DatagramPacket requestPacket = new DatagramPacket(new byte[1024],1024);
            // 2. 接收数据
            socket.receive(requestPacket);
            // 3. 解析接收到的数据
            String request = new String(requestPacket.getData(),0,requestPacket.getLength(), StandardCharsets.UTF_8);
            // 4. 根据请求来计算响应
            String response = process(request);
            // 5. 使用DatagramPacket封装响应数据
            DatagramPacket responsePacket = new DatagramPacket(response.getBytes(StandardCharsets.UTF_8),
                    response.length(),requestPacket.getSocketAddress());
            //6.发送响应
            socket.send(responsePacket);
            // 7. 打印日志
            System.out.printf("[%s:%d] request = %s, response = %s\n", requestPacket.getAddress().toString(),
                    requestPacket.getPort(), request, response);
        }
    }

    protected String process(String request) {
        return  request;
    }

    public static void main(String[] args) throws IOException {
        UDPEchoServer udpEchoServer = new UDPEchoServer(9090);
        udpEchoServer.start();

    }

}
